Formulation Requirements of Topical Delivery Systems

Abstract

The formulation of topical medication bases must inevitably respond to restrictions imposed by a number or physical properties of the medication itself (solubility, pH stability, ionic activity, etc.) as well as to various auxiliary effects desired, such as skin pemeability or non-permeability, resistance to wash-off or ease of wash-off, speed of release of the drug, etc. All such factors determine the “formulation environment” to be provided for the active ingredient, in which it must then be tested for shelf-life stability, pharmacologic activity and safety.

Once the basic requirements have been determined for the formulation, it becomes relatively simple to set a “formulation profile” for the product whether it shall be an anhydrous ointment or W/O or O/Wemulsion; whether encapsulation or other techniques are required to provide “timed release” of the active ingredient(s); the type of preservative required; to what degree side-effects of the drug can be altered by various formulation techniques; and whether the active ingredient's keratin substantivity can (or should) be altered by modification of the base vehicle.